Canon NP6251 Service Manual page 639

CHAPTER 11 TROUBLESHOOTING
39. The scanner fails to move forward.
Cause Step
Cable
Scanner path
Scanner motor
(M3)
DC controller
PCB
40. The scanner fails to move in reverse.
Cause Step
DC controller
PCB
Scanner motor
(M3)
11-108
COPYRIGHT © 1997 CANON INC.
Checks
1 Is the scanner drive cable routed
correctly?
2 Is the scanner rail free of dirt?
Does the scanner move smoothly
when pushed by hand?
3 Set the meter to the 12VDC
range, and connect the probes of
the meter to the terminals shown.
Does the voltage change when
the Copy Start key is pressed?
+ –
M3ON J112B-6 J112B-3
M3F/R J112B-7 J112B-3
Checks
1 Does the scanner move forward?
2 Set the meter to the 12 VDC
range. Does the voltage between
J112B-7 (+) and J112B-3 (–) on
the scanner controller PCB
change to about 5 V when the
scanner stops moving forward?
YES/NO
NO
NO
YES
NO
Voltage
about 0 to 5 V
about 0 to
about 5 to 0 V
YES/NO
NO
NO
YES
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
Action
Route the cable
correctly.
Is the surface of the
scanner rail soiled? Is
there foreign object that
comes into contact with
the scanner. As
necessary, clean,
lubricate, or correct.
Reference:
If the surface of the rail
is soiled, clean it with
alcohol, and apply a
small amount of
lubricant.
Replace the scanner.
motor.
Check the wiring from
the DC controller PCB to
the scanner motor; if
normal, replace the DC
controller
Action
See "The scanner fails
to move forward."
Replace the DC
controller PCB.
Check the wiring from
the DC controller PCB to
the scanner motor; if
normal, replace the
scanner motor.